It has heretofore been known, as disclosed in J. American Chemical Society, Vol. 85, pp. 485-6 (Weiner and West, 1973), in the article entitled "Complex Formation Between Ethyllithium and t-Butyllithium", to produce complexes of ethyllithium and t-butyllithium by dissolving ethyllithium and t-butyllithium in benzene. This article points out that ethyllithium alone is sparingly soluble in cold benzene (generally speaking, ethyllithium has a solubility of 0.2 N in n-hexane and somewhat higher in cyclohexane at room temperature) but its solubility is greatly enhanced when the benzene solution contains t-butyllithium; and that the solution of the ethyllithium and the t-butyllithium forms a complex in which both the ethyl and t-butyl groups are bonded to lithium. The complexes are stated to be believed to be electron-deficient polymers of the type (EtLi).sub.n (t-BuLi).sub.m-n, where m is a small number such as 4 or 6.
The said article further points out that, when benzene from a benzene solution of ethyllithium and t-butyllithium is evaporated, a low melting white solid residue is obtained which is highly soluble in pentane, unlike ethyllithium which is virtually insoluble in pentane; that the ratio of ethyl to t-butyl groups in the resublimed complex is nearly the same as in the original benzene solution; and that 1:1 ratios, as well as 1.8:1 ratios, of the ethyllithium to the t-butyllithium produced, on distillation, distilled products with ethyl: t-butyl ratios of 1.1:1 and 1.7:1, respectively, m.p. 68.degree.-72.degree. C. and 56.degree.-59.degree. C. Benzene solutions specifically containing 8 wt. % each of ethyllithium and t-butyllithium are disclosed in said article.
Finally, the aforesaid article states that it was not known whether the formation of mixed organolithium compounds will occur generally, but that preliminary results indicate that t-butyllithium enhances the solubility of phenyllithium in benzene, but only to a limited extent. No uses or utilities are disclosed or suggested for the complexes of the ethyllithium and t-butyllithium or the benzene or pentane solutions thereof; or, for that matter, of the very generally disclosed phenyllithium solutions in benzene to which t-butyllithium was added.
As is pointed out in the article by Weiner, Vogel and West entitled "The Physical Properties and Structure of t-Butyllithium", Inorganic Chemistry, Volume 1, No. 3, August, 1962, pure t-butyllithium is a colorless crystalline solid, readily soluble in hydrocarbon solvents. Solutions of pure t-butyllithium in refluxing n-heptane turn brown and deposit a precipitate after about an hour, indicating that noticeable decomposition occurs during this time. A comparison is referred to with ethyllithium in relation to the degree of association, and it is stated that the average degree of association of t-butyllithium is very nearly four over a considerable range of concentrations in solutions in benzene and n-hexane, whereas the average degree of association in benzene solutions for ethyllithium is about six.
It has also been known to the art to prepare complexes (a) of ethyllithium with polyisoprenyllithium, (b) of n-butyllithium with isoprenyllithium, (c) of sec-butyllithium and polyisoprenyllithium, and, generally, of corresponding complexes where polystyryllithium was used in place of polyisoprenyllithium, in liquid hydrocarbon solvents such as benzene and n-hexane, Macromolecules, Vol. 3, No. 3, May, June, 1970, pp. 333-337, article entitled "The Cross-Association of Polyisoprenyllithium with Ethyllithium", Morton, Patt and Fetters. These complexes have been prepared in connection with studies dealing with association phenomena in organolithium polymerizations in hydrocarbon solvents based upon the possibility of cross-association between the propagating polymer-lithium species and any residual alkyllithium initiator since this could lead to complex kinetics in both the initiation and propagation reactions. Such studies were based upon concentration solution viscosity measurements. The authors reach the conclusion that the following association equilibrium can be written for this system: EQU (RM.sub.2 Li).sub.2 +(EtLi).revreaction.2RM;Li.(EtLi).sub.3
and that in the polymerization reaction preferential cross-association occurs.
Furthermore, it has been known, as disclosed in U.S. Pat. No. 3,452,111, patented June 24, 1969 on an application filed Dec. 9, 1966, which patent was issued to and is owned by the Assignee (now by change of name, etc., to Lithium Corporation of America, a Delaware corporation) of the present application, that the stability against decomposition of sec-butyllithium and other heat labile secondary alkyllithiums, notably those containing from 4 to 8 carbon atoms in the alkyl radicals, generally in the form of solutions thereof in inert organic solvents, can be substantially increased by the addition thereto of variable proportions specifically of isopropyllithium and/or n-butyllithium. This patent does not deal in any way with ethyllithium, makes no reference whatever to the enhancement of the solubility of ethyllithium in inert organic solvent solutions thereof by the addition thereto of sec-butyllithium (or, for that matter, by the addition thereto of n-butyllithium or of isopropyllithium), or to the enhancement of the stability of sec-butyllithium or n-butyllithium or isopropyllithium by the addition thereto or the admixture therewith of ethyllithium, and said patent never contemplated the discoveries to which the present invention is directed.
It has also heretofore long been known and disclosed in numerous patents in connection with the preparation of homopolymers as well as copolymers of butadienes such as 1,3-butadiene; isoprene; vinyl-substituted hydrocarbons; vinyl halides; vinylidene halides; esters of acrylic acid; esters of homologs of acrylic acid, and numerous other polymerizable monomers; as well as in the preparation of telomers, to utilize, as catalysts or initiators in such polymerization and telomerization reactions, metallic lithium; lithium hydrocarbons; alkyllithiums corresponding to the formula R(Li).sub.x where R is a saturated or unsaturated hydrocarbon radical selected from the group consisting of aliphatic, cycloaliphatic, aralkyl, alkaryl, and aromatic radicals, and x is an integer from 1 to 4, inclusive, and wherein the R group has a valence equal to the integer x and preferably contains from 1 to 20 carbon atoms. Examples thereof are methyllithium, ethyllithium, isopropyllithium, n-butyllithium, amyllithium, hexyllithium, t-octyllithium, cyclohexyllithium, s-butyllithium, t-butyllithium, and t-amyllithium, phenyllithium, tolyllithiums, xylyllithiums, alpha-and beta-naphthyllithiums, allyllithium, methallyllithium; hydrocarbon polylithium compounds such as methylene dilithium, ethylene dilithium, trimethylene dilithium, octadecamethylene dilithium, and 1,2-dilithium propane; polylithium aryl, aralkyl and alkaryl compounds such as 1,4-dilithium benzene, 1,5-dilithium naphthalene, 1,2-dilithium-1,3-diphenyl propane; tri and higher lithium hydrocarbons such as 1,3,5-trilithium pentane and 1,3,5-trilithium benzene.
The foregoing organolithium compounds are disclosed in, among other patents, U.S. Pat. Nos. 2,975,160; 3,065,218; 3,094,512; 3,231,635; 3,294,768; 3,297,793; 3,301,840; 3,317,918; 3,324,191; 3,332,856; 3,427,364; 3,449,306; 3,464,961; 3,465,065; 3,498,960; 3,513,056; 3,554,911; 3,558,575; 3,607,846; 3,652,516; 3,692,874; 3,742,077; 3,752,501; 3,760,025; 3,787,377; 3,840,616; 4,057,601; 4,076,914; and 4,237,245; Canadian Patent No. 750,006; and Australian Patent No. 262,782. The general statement is made in some of these patents, after listing many of the aforesaid organolithium compounds, including unsaturated organolithium compounds and aryl, aralkyl and alkaryl lithium compounds such as allyllithium, methallyllithium, phenyllithium, tolyllithiums, xylyllithiums and naphthyllithiums, that mixtures of such organolithium compounds can be used, but no particular examples of any such mixtures are given. Illustrative of such patents are U.S. Pat. Nos. 3,506,631 and 3,632,563; and British Pat. Nos. 817,693; 817,695; and 994,726. None of these patents provides any concept or teachings which would lead one versed in the art to my present invention and the important benefits which result therefrom.
With due regard for the foregoing disclosures in the above-enumerated patents concerning the uses, as catalysts or initiators, of any of large numbers of different organolithium compounds in polymerization and other reactions, or, as noted above, very generally stated mixtures of such organolithium compounds, it will be seen from said patents that, in practically all of them, in the actual disclosed working examples, with very minor exceptions, n-butyllithium is the catalyst or initiator of choice. This is because it has been found to be, with very limited exceptions, the most desirable organolithium compound from the overall standpoints of its effectiveness utility-wise for the intended reactions, its relative ease of handling, manufacture and for other reasons as well.